The present invention relates to an apparatus to be used in a well structure for testing a blowout preventer under substantial pressures wherein the pressure is exerted under the closed blowout preventer by sealing across the upper end of the hanger. With deep wells having a substantial string suspended from the hanger, the loading of the hanger landing shoulder on the housing landing seat is very substantial and the pressure loading above the hanger increases the landing seat loading well above its design point so that testing pressures will result in a failure of the landing shoulder or seat, damage to the hanger and housing and other future problems in the well.
U.S. Pat. No. 2,540,322 discloses the use of a packing seal on the drill string to allow pressure to be diverted into the casing above the packing seal for the testing of the blowout preventer.
U.S. Pat. No. 3,897,824 discloses an annular structure mounted on a string which is lowered through a blowout preventer which seals against the casing, includes passages extending axially through the structure and has a valve plate which is lowered by the string to close the passages whereby test pressure builds up above the structure to test the sealing of the blowout preventer. The testing load of the structure is transferred to the upper end of the hanger seal assembly.
U.S. Pat. No. 3,093,996 discloses another blowout preventer tester which is lowered through an open preventer and seals on the taper of the casing head to deliver pressure thereabove for the testing of the closed blowout preventer.
U.S. Pat. No. 4,090,395 discloses a structure which includes the lowering of a seal onto the upper end of the hanger for sealing across the bore of the well head and the string on which it is lowered delivers pressure to the space above the seal and below the closed blowout preventer. In this structure the pressure load, if not supported by the string is transferred directly to the hanger landing shoulder and the wellhead seat on which the hanger landing shoulder is landed.
None of these prior structures provides the capability for high pressure blowout preventer testing i. e., 15,000 psi. They do not avoid the imposition of the pressure load through the hanger landing shoulder to the housing seat.